rexford

The British tests conducted at 610 m/s to compare projectile penetration resulted in )going by memory here and it is 4am, so please excuse small deviations from actual): 17 pounder APCBC 109mm German 75mm APCBC 101mm U.S. 76mm APCBC 90mm Russian 76.2mm APBC 75mm Miles Krogfus published test results in AFV News on AP performance during WW II. 17 pounder APCBC outpenetrates U.S. 76mm APCBC by a large margin, but 17 pounder has some advantages, it is solid shot and weights more than U.S. 76mm APCBC. Having an HE filler generally decreases penetration by about 10% or so, based on our studies. And 17 pounder outweighs U.S. 76mm by 17 to 15.44 pounds. If 17 pounder round weighted 15.44 pounds and had an HE filler the penetration at 610 m/s would decrease to: 109 x (15.44/17)^.7143 x (.90), or about 92mm. This shows that British APCBC and American APCBC had about the same penetration characteristics when weight and HE filler differences were sorted out. Analysis of 2, 6 and 17 pounder AP penetration and comparison with U.S. AP shows similar results, 2 pounder and 6 pounder AP penetrate with about the same "K" factor. U.S. curves for 57mm solid shot AP result in similar penetration figures as British 6 pounder AP, and when we used the U.S. 57mm AP penetration against face-hardened armor to predict 6 pounder AP performance during actual tests against German panzers, the 57mm AP data matched the penetration ranges. So German APCBC outpenetrates British APCBC by about the same margin as U.S. APCBC. Regarding nose hardness characteristics of British APCBC, tests showed that 6 pounder APCBC would shatter and fail when it hit less face-hardened thickness than it could penetrate on half the hits at a given velocity, which is "shatter gap". In North Africa, 2 pounder AP hits on panzers would fail at close range and penetrate further out, or would have a gap in the penetration range (defeat armor to 600 yards, fail from 600 to 900 yards, and then penetrate again out to 1200 yards). When rounds with nose hardnesses within a certain range overpenetrate armor by certain ranges, as armor is thrown out of the way at faster rates the nose pressure builds and the nose absorbs energy. When energy absorption exceeds certain levels the projectile nose shatters and hits fail. The British thought that putting armor piercing caps on AP rounds would prevent shatter gap, but test results suggest that it didn't. U.S. 76mm APCBC test results follow against 3" armor at 30°: Impact at 1954 fps, plate bulge 2065 fps, complete penetration 2073 fps, base of round sticks in plate, rest of round passes through 2160 fps, projectile sticks in plate 2205 fps, projectile splits in two and fails to pass through armor 2376 fps, projectile breaks up and fails to pass through plate More is not always better when it comes to penetrating armor. Actual tests of 6 pounder AP against Tiger side armor in North Africa showed shatter gap failure when the penetration exceeded armor resistance within certain ranges. 6 pounder AP knocked out some Tigers in the initial combat in Africa, if the range had been shorter the hits may have failed, which is contrary to what one would expect. British 6 pounder APCBC would penetrate about 76mm of homogeneous armor at 610 m/s, U.S. 57mm APCBC penetration at that velocity is 70mm. Analysis also suggests that British and American penetration test plate had about the same resistance, and good quality armor from both countries was similar and about the same as good quality German armor. It is also important to note that tungsten rounds will fail against armor that is well below the listed penetration if the impact velocity and impact angle are within certain limits. British lab tests predicted certain results, and tests of APDS against Tiger armor showed that tungsten shatter gap occurred. Just because APDS penetrates alot of armor doesn't mean it won't fail against relatively thin armor (compared to penetration figure). U.S. HVAP tungsten rounds generally strike at velocities where shatter gap is less of a problem, the high velocity of APDS creates more chances for shatter failure.

German use of face-hardened armor on panzers through October 1944 had a significant impact on the vulnerability of tanks to Allied APCBC projectiles. Panther A carried face-hardened side hull plates, and PzKpfw IVH and StuG IIIG used face-hardened frontal armor. While Sherman 75mm APCBC is often maligned due to 81mm homogeneous penetration at 500m, which severely limits effectiveness against the ultimate Sherman nemesis, Tiger E, that round could defeat 95mm of face-hardened (FH) plate at 500m. Against a Panther on a flank hull shot, the ability to penetrate 95mm effective armor (FH) at 500m allows a much greater arc from armor facing for effective 75mm Sherman shots. The effective range of 75mm APCBC against the front hull of PzKpfw IVH and StuG IIIG also increases greatly due to FH armor use. German use of face-hardened armor till late in the war was probably predicated on Russian use of uncapped rounds (no armor piercing cap), which lessened effectiveness against the very hard surface layer on FH armor.

During WW II, German tank effectiveness was due in large part to the superior effectiveness of the ammunition, which is related to nose hardness considerations. British tests against homogeneous armor at 610 m/s impact velocity, which are documented in Miles Krogfus' AFV News article, resulted in: 102mm penetration for German 75mm APCBC 90mm penetration for U.S. 76mm APCBC 75mm penetration for Russian 76mm APBC U.S. penetration tests for Sherman 75mm indicate 89mm penetration at 610 m/s. Based on the above figure at 610 m/s, the Panther 75mm penetration is estimated at 188mm at 935 m/s and 0m range (DeMarre equation extrapolation). Actual U.S. tests with Panther 75mm APCBC obtained 190mm penetration at 0m and 935 m/s impact. German projectile nose hardness advantage over U.S. APCBC, 61 to 54.5 Rockwell C Hardness, also assured that German hits were outside "shatter gap" region. During U.S. tests with 76mm APCBC, hits that overpenetrated armor resistance by 5% to 25% would FAIL due to shatter when results exceeded certain velocity and armor thickness figures. It turns out that low nose hardness results in excessive energy absorption when round overpenetrates armor, and nose may crack and break-up.

While U.S. HVAP boosted penetration of 76mm and 90mm guns against near vertical armor, tungsten rounds have much higher slope effects which decreased HVAP performance against many panzers. HVAP Penetration at 100m, 500m and 1000m: 76mm: 239, 208, 175 90mm: 306, 278, 246 Panzer glacis and front superstructure resistance to HVAP hits is computed below: Hetzer (60mm at 60°): 263mm at 0° Panther (85mm at 55°): 289mm at 0° Tiger II (150mm at 50°): 413mm at 0° JgPz IV (60mm at 50°): 165mm at 0° JgPzIV (80mm at 50°): 220mm at 0° In comparison, Hetzer 60mm at 60° armor resists 90m APCBC hits like a 165mm thick vertical plate.

Using the data and procedures in our book on WW II BALLISTICS, we prepared front hull resistance stats for the different Sherman models (and Pershing), based on cast armor deficiency to rolled plate and assumption that tanks built prior to October 1943 had flawed armor (that date marks the required use of improved quality control and heat treatment processes in U.S. armor manufacturing). Resistance is keyed to 75mm APCBC hits and would be somewhat lower on 88mm APCBC hits: M4, M4A2, M4A3, M4A4 (56° glacis) 104mm for rolled glacis plates 100mm for cast glacis plates 100mm for upper nose M4A1 Early 84mm to 92mm glacis 72mm driver and bow MG hood areas 152mm at glacis outer edges 100mm upper nose M4A1(76)W 88mm to 100mm glacis 76mm driver hood 100mm bow MG hood 164mm at glacis outer edges M4A3E8, M4A3(75)W, M4A3(76)W 116mm glacis 108mm upper nose PERSHING 104mm upper glacis center (20° slope) 184mm glacis 160mm nose German battle reports indicated that 75L48 on PzKpfw IVH and StuG IIIG could not penetrate 47° glacis armor at 1000 meters. Actual range would be much less. --------------------------------------------- By way of comparison, PANTHER 220mm unflawed Glacis 208mm flawed glacis 156mm nose TIGER E 104mm driver plate 284mm glacis 116mm nose ---------------------------------------------- Interesting point is that Shermans with 47° glacis present greater resistance to 75mm hits than Tiger E. Barring a critical hit (round strikes bow machine gun ball, weld lines at glacis/nose intersection or armor edges), 17 pounder APCBC will not penetrate Panther glacis armor based on computed armor figures. This is consistent with actual firing tests conducted by British and American forces. Interesting result from U.S. tests at Isigny France during August 1944 is that 17 pounder APCBC won't penetrate Panther glacis at 200 yards, but it may crack brittle armor. Once Panther glacis is cracked, edge effects lower resistance to less than 70% of full effect, and 17 pounder APCBC hits near or on a crack could and did penetrate.

This post and following additions contain some recent work regarding the capability and armor resistance of Sherman tanks and U.S. armor piercing weapons and ammo. The material summarizes (and in some cases belabors) the data in our book. ------------------------------------------- Using the curves and procedures in our book on WW II BALLISTICS, we analyzed the effective resistance of the M34A1 gun mount against 75mm APCBC using modifiers for slope effect, cast armor deficiency to rolled plate, flaws edge effects and spaced armor. The following is a breakdown of the armor resistances (0° effective) based on random distribution of hits against the gun mount on 56° glacis Shermans and Fireflies: 8% hit 45mm effective resistance 6% hit 65mm 22% hit 75mm 25% hit 85mm 18% hit 95mm 6% hit 105mm 4% hit 115mm 3% hit 125mm 4% hit 145mm 1% hit 155mm 3% hit 165mm The average armor resistance is about 89mm. Against 75mm armed Shermans with 47° glacis plates (unflawed armor), armor resistance would be about 5% higher. While some of the figures suggest very good resistance on some hits, the spaced nature of the two shields results in a phenomenom called keying, where the outer shield is fully penetrated and the round sticks in the inner shield, which freezes the gun elevation system. Our calculations indicate that almost every 75mm and 88mm projectile hit on the M34A1 gun mount will fully penetrate the outer shield, which creates a large number of situations where hits that should be defeated are able to create some damage to the gun system. The low armor resistance figures are due in many cases to openings in the inner shield and edge effect considerations. [ 09-14-2001: Message edited by: rexford ]

Originally posted by PondScum: CMBO rifle grenade penetration has been quoted as 60mm@0 degrees, and tested to penetrate 51mm@40 and 30mm@60, but failed to penetrate 54mm@45, 45mm@55, and 51mm@60 (thanks to Chris Hare for this). What figures do WW II sources give for U.S. rifle grenade penetration?

How much armor thickness can a rifle grenade penetrate? Can a hit by a rifle grenade penetrate the Tiger side 60mm or 80mm?

On level ground, at 300m with 85% armor quality, 75mm armed Sherman has no real chance to penetrate Hetzer 60mm at 60°. Of course, a hit at intersection of upper and lower hull would face reduced resistance.

75mm armed Sherman will not routinely penetrate 60mm armor at 50° slope with 85% armor quality at 250 meters. There is a small probability at above stated conditions due to standard probability of penetration statistics. But chances will be about 1 in 6. And that's with a 10° downward angle from firer to target. If angle is smaller probability approaches 0%. [ 09-08-2001: Message edited by: rexford ]

The Mycenius site has a British armament ammo allocation breakdown, the 75mm APCBC details are interesting: 75mm APCBC M61-HE filled 75mm APCBC M61-Inert filled An assorted mix of the two types of 75mm M61 ammo is to be carried adding up to about 35% of total load. No M72 solid shot 75mm ammo is identified as being used. This page suggests that British used a combination of 75mm APCBC rounds, HE and inert filled. Since this ammo breakdown 17 pounder APDS and 77mm projectiles, it would be very late war. The ammo breakdowns for 76mm M62 projectiles used in U.S. gun are identified as inert filled, with no HE filled rounds. 75mm HE is Super version fired at 1980 fps, while normal 75mm HE (fired at 1515 fps) is not carried. Mycenius address is http:/members.nbci.com/_XMCM/mycenius/weapons/armour3.html [ 08-31-2001: Message edited by: rexford ]

I wouldn't be surprised if British didn't stop 75mm tests at 38 shots because increase in targets damaged with additional shots had stopped. If logic in last few posts holds, then ricochet 105mm impacts about twice the targets as 75mm, and instantaneous burst 25 pounder HE impacts almost as many as ricochet 105. British report also adds that airburst rounds are no more effective than groundburst against targets in slit trenches despite theoretical 2:1 advantage in effective fragments.

It took awhile but it came through the daze I have been in these last few days. If 75mm HE rounds were fired under same conditions as 105mm, but only 33 targets were effectively hit, then there is no reason to believe that taking more shots would add targets. In other words, first 38 shots by 105mm probably penetrated around 65 targets, and next 62 shots kept hitting same targets over and over again. (if 105mm took 1000 shots, number of impacted targets would still be about 65 but percentage would be so low 20mm HE would look more effective) So 105mm might impact twice the targets as 75mm, which would seem reasonable. Got it, and appreciate your patience. Now, 75mm has about the same lethal radius as 105mm, which is interesting. This suggests that 75mm effective fragment density is less than 105mm (about half) but reaches out to almost the same distance. Finally, British reports show that slower HE rounds are more accurate. Thanks for comments, which I will be sure to add to my HE comments on other sites. My grandmother called me a hardhead, and this may be true more than I care to admit.

The key question when it comes to area coverage for ricochet fire test is whether 75mm HE would hit at least 65 targets effectively if it were given 62 more shots. Were the 33 targets that were critically hit by 75mm HE the most that could be hit, and would adding more shots add to the hit total?

The Panther vs Panzerfaust analogy is way off base, is not correct and misses the point. We're talking area coverage here, for 75mm vs 105mm HE, so hitting the same point repeatedly is expected. And is okay. 75mm ricochet HE hits a larger number of targets effectively than 105mm, per each shot, which implies greater area coverage for effective shots. 105mm may hit more targets per shot, but 75mm hits more targets effectively per shot. A critical distinction.

I would also note that the previous comments on my analysis overlooked the similarity of the lethal areas for 75mm and 105mm HE using ricochet fire. This is very surprising and is not consistent with test results for ground blasts, so is something new that the statistical naysayers overlook in their griping. And it is surprising. Definition of lethal blast area requires that results from individual shots be analyzed, a point I made in past posts which seems to have been passed over. Ricochet fire is not ground blast, and it is quite possible that 75mm HE has advantages over 105mm that show up in ricochet tests and do not show up in ground blast tests. So the surprise is due to different conditions for explosion location, and it may not be proper to use ground blast data to predict performance of ricochet fire. If 75mm has smaller lethal area than 105mm and 75mm critically hits more targets per round, than this suggests that 75mm is putting out a higher number of effective fragments per round during ricochet fire. Which suggests that ground blast data does not hold during ricochet fire. Which is a very important and surprising result/theory, and places some common assumptions in doubt. That is why I made such a big deal out of 75mm being more effective than 105mm, because it is totally out of line with what we expect. I expected 75mm to be inferior to 105mm, to tell the truth.

We really don't know how shots were distributed over the target area with regard to changes in ground aim point or lateral distribution, so definite conclusions are not possible. If 38 rounds from 75mm gun are distributed in same proportion and area as 105mm, then 75mm HE averages a greater number of effective hits per shot than 105mm. So, if shots in field during combat are distributed in accordance with test results and targets are distributed in same manner as wooden targets, 75mm HE using ricochet fire has higher probability of successfully penetrating an infantry target. 105mm has higher chance of hitting someone, but 75mm has higher chance of doing something bad to someone. It doesn't matter much if targets are hit repeatedly, since the test measures how many different targets were hit and/or incapacitated, which is a function of statistical area coverage. 75mm HE incapacitated 33 targets with 38 shots, 105mm HE did in 65 targets with 100 shots. If distribution of shots is similar, 75mm has higher statistical probability of doing something useful. I would assume that British were smart enough to make sure that 38 rounds from 75mm HE were distributed in similar fashion to 100 rounds from 105mm. If that is case, test results can be compared and analyzed statistically. And 75mm HE outperforms 105mm. Responding to an earlier comment: Regarding ricochet height and aim point, these are very important since number of effective fragments is very dependent on distance and angle from explosion.

Ricochet fire data shows that 105mm HE is better than 75mm at hitting things, 95% to 80%, but 75mm is better at incapacitating targets, 87% to 65%. Means that 75mm frags have more penetration than 105mm, and more velocity at impact. 75mm HE is simply the best!

Ah, but it is worth making conclusions about, which is what the scientific method is all about, isn't it? Get some data, draw a hypothesis even if data is limited, and go after more to see if original theory holds water. We have made some considerable discoveries by taking limited data that really doesn't appear to support a theory with any real mathematical certainty, producing a theory and mathematical relationship and then going after data to test the theory. In some cases the original theory is crap, in many others the original conclusion holds really well. Drawing a conclusion from limited data is a research aid that focuses attention and is a valuable approach. I have been doing research for over thirty years and use the above noted approach all the time. I guess that the approach we use may not come across as valid to some readers, but it works well from our angle. Unconventional, but has paid dividends. It is also more beneficial to explore possibilities than to gripe over limited data.

It is true that one can't say for certain that 100 75mm HE shots would penetrate "100/38" times as many boards. The interesting point is that the Sherman 75mm is so close to 105mm HE. Note the lethal area for 75mm and 105mm HE using ricochet fire is very close, a few feet difference in radius. Lethal radius would have to be determined from a single shot, more or less. Or so it would seem. Note also that 75mm HE gets more wooden targets incapacitated per effective round than 105mm. So 75mm seems to be spraying fragments around better (29 effective rounds, 33 targets hit with effective fragments). Since we don't know the ranges of the tests, the projectile height above ground, and range settings and variations, etc., definite conclusions are impossible to make. But the fact that 75mm HE is close to or superior to 105mm HE in any respect, even with fewer shots and extrapolation of results, is very surprising. This suggests that ricochet fire may introduce some factors that we did not previously consider, since everything else says that 105mm HE is worlds above 75mm HE. Statistics aside for the moment, when 75mm HE outperforms 105mm HE in a ricochet fire test it seems important enough to take note of. This is a highly unusual result. The other test result, where slower 75mm HE is more accurate than higher speed HE against ground point targets (less horizontal dispersion), confirms what the Germans and our group calculated. Higher velocity HE has greater ground scatter, which can sometimes be good but can also be less effective against a small group far from others.

We just came across this HE test data. Granted that the test parameters are barely mentioned, but the results still show 75mm HE being very effective on ricochet shots. If new targets put out for each gun and perforated targets are identified after all the rounds are fired, guns with more rounds may penetrate targets many times. But results still show 75mm hitting more targets per round than 105mm. If all guns had fired 100 rounds the results would probably be more comparable, but even then we don't know how range estimates and ground aim was varied. Still, 75mm HE may be equal to or better than 105mm HE at casualty causation due to factors we have not identified. 25 pounder HE about the same HE filler weight as 75mm HE, 1.75 vs 1.70 pounds, but 75mm has lower total weight. So 75mm probably puts out a greater number of effective fragments (equal explosion blows 75mm shell into more small pieces travelling at higher velocities). The fact that 75mm HE outperformed 105mm HE in a test suggests much. Also note that lethal radius of 75mm is only slightly smaller than 105mm HE, 28' vs 31'. Lethal radius data suggests that each shot may have been analyzed separately. I'll try to obtain entire report to see if key data is presented.

British reports WO 291/113 and WO 291/146 are presented on the John Salt site and provide the following results: 1. Ricochet fire effectiveness A. 105mm with delay 100 rounds fired, 95 effective, 65 wooden targets hit and incapacitated (65% for effective target hits/rounds fired) B. 75mm with delay 38 rounds fired, 29 effective, 33 wooden targets hit and incapacitated (87% for effective target hits/rounds fired) C. 25 pounder 100 rounds fired, 82 effective, 26 wooden targets hit and incapacitated (26% for effective target hits/rounds fired) D. 25 pounder (timed airburst) 100 rounds fired, 85 effective, 9 wooden targets hit and incapacitated (9%) 2. Lethal areas for each round 25 pounder timed airburst 240 sq ft 105mm ricochet 3000 sq ft 75mm ricochet 2500 sq ft 25 pounder ricochet 720 sq ft 3. Impact of Velocity Upon HE Accuracy Normal 75mm HE has 90% horizontal zone of 35.5 yards for distance dispersion Super 75mm HE has 90% horizontal zone of 59 yards for distance dispersion Increasing 75mm HE muzzle velocity increases the ground scatter, which reduces accuracy against ground point targets. 4. 25 pounder performance increased when instantaneous DA was used, 200 rounds, 159 effective, 61 targets incapacitated (30.5%) and lethal area of 2300 sq ft. 5. Firing test used wooden targets in a 9 x 9 grid 100 yards wide and 150 yards deep. 6. 75mm HE outperforms 105mm HE during ricochet firing tests in terms of casualties per round fired. 7. Slower 75mm HE appears to be more accurate against ground points in terms of getting a higher percentage of the shots within a given distance of the target point.

The War Games Rules 1925-1950 ruleset has some interesting notes on smoke usage: 1. smoke screens cannot mature in still air or high winds 2. smoke obscures rather than blocks LOS if sighting through an artillery beaten zone where one battery gun is laying smoke screen

Advanced Squad Leader treated smoke in an unusual manner, it did not totally rule out line of sight to targets but lowered the hit probability. The thinking was that smoke did not produce a tight blanket of sight limiting cloud, but a relatively broken "mass". Depending on random factors, one could either see nothing or see the world. Smoke was also treated as a limited use/availability ammunition. Sherman 75mm gun would have smoke 28% of first attempt tries during June 1944, and white phosphorus (WP) during 58% of first tries. U.S. 81mm mortar would have 72% first attempt availability with WP, no mention of smoke rounds. U.S. 60mm mortar fires WP with 58% and 42% first try availability. White phosphorus in ASL was less effective than smoke in hindering LOS and hit probability. Smoke and WP effect could be increased by firing different weapons at the same target, which would "add" modifiers.

Ten shots at the suspension of the Panther is one notable result in that terrific relating of combat. The other is the use of Sherman 75mm or M-10 76mm HE shells to button tanks and possibly disrupt their optics. One of the threads on the G104 Sherman forum discussed how British Shermans were supposed to draw fire and use their HE to: A. knock out German heavy tank suspension, tracks or drive wheel B. Button up German tank C. Disrupt panzer optics D. Divert attention from Firefly Several of the above noted objectives would be gained by aiming HE at the turret, since AP failure was assumed. Firefly would be in hiding just behind lines, ready to spring into action upon call. The use of HE fire to reduce panzer effectiveness, and shots at the suspension, are tactics that are often missing in tactical level wargames. Russian story on Battlefield site has TWO 75mm armed Shermans knocking out Tigers, first tank shoots out a track and second tank blasts the side armor as the Tiger rotates on one track. As noted in the opening post on this thread, infantry-artillery-tank actions in close country create a different set of rules, and a few "superior" tanks are not enough to turn things around. Breaking through lines with tanks and failing to hold ground does nothing. Thanks for an excellent research effort, Jason.